Electromagnet



.June 3, 1930- P. TRoMBl-:TTA l1,761,759.

f ELEGTROMAGNET Filed Jan. 15, 1929 Inventor' bg] MMI/70mm pclnLLo. Trombetta,

Patented June 3, 1930 UNITED STATES PATENT OFFICE PANFILO TROMBETTA, FMILWAUKEE, WISCONSIN, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK ELECTROMAGNET Application led January 15, 1929.Serial No. 332,634.

My invention relates to electromagnets, more particularly toelectromagnets energized by alternating current, and has for its objectthe provision of an improved device of this character in which asubstantially J uniform pulling force will be obtained.

In general, electromagnets operated with alternating current have beensubject to a disadvantage due to the vibration of the armature or otherarticle being held by the magnet. In many instances, as in the case oflifting magnets, electromagnetic brakes and chucks, the vibration of thematerial being held is often dangerous and at least detrimental to theefficient operation of the device.' It is the purpose of my invention,therefore, to provide an electromagnetic device which may be operatedwithV alternating current and bymeans of which the article or articlesto be held will be attracted to the magnet by a pulling force which issubstantially as constant as that which could be obtained by the use ofdirect current.

With this object in view, in carrying out `my invention I have providedan electromagnet having a distributed, polyphase Winding, this windingbeing arranged to produce a flux which moves substantially transverselyof the direction of constant pull. Since the field distribution in acore having a polyphase winding is sinusoidal and does not change invalue while the field moves across the core, it follows that the pullexerted in a direction normal to the core is constant and thereforethere is no vibration or chattering between theyarticle being held andthe magnet.

The invention will be better understood from the following descriptiontaken in oo nnection with the accompanying drawing and its scope will bepointed out in theappended claims.

In the drawing Fig. 1 is aside elevation of an electromagnet Vembodyingthe `invention in one form. 'Fig 2 is a view taken along the line'2-2 ofFig. 1 looking in the direction of the arrows, and showingdiagrammatically `the electrical connections to the winding; Fig. 3 is aside elevation of an electromagnet embodying a modication of theinvention; Fig. 4 is a view taken along the line 44.of Fig. 3 looking inthe direction of the arrows, and Figs. 5 and 6 are diagrammaticrepresentations of the flux produced at different instants by the wind.-ing shown in Figs. 1 and 2.

Referring to Figs. 1, 2, 5 and 6 of the drawing, I have disclosed oneform of my invention as embodied' in a magnet having a fixed or statormember 10 and a movabie armature member 11. The stator member 10comprises L-shaped bracket members 12 and 13 which serve to support acore 14, this core 14 being preferably formed of a plurality oflaminations as is shown more clearly in Fig. 2. It will be noted thatthe core 14 has a concave face in which are provided a plurality ofslots 15. The armature member 11 comprises a pair of strips 16, 16 whichserve to support anv armature' 17. The strips 16, 16 are suspended frompivot supports 18 in such a manner that the armature' 17 may readilyswing toward and away from the concave face of the core 14. The armature17 is also preferably laminated. The portion of the armature nearest thecore 14 has a convex shape7 curvature of this con* veX face and thecurvature of the concave face of the core 14 being substantially thesame, so that the armature 17 may lie closely adjacent the core 14. Arod or strip 19 is pivotally attached to the lower ends of the strips 16and serves to transmit motion from the armature 17 to a member or deviceto be controlled. i

In accordance withmy invention, I have provided a winding 20 suitablysecured in the slots 15 of the core 14 and as will be observed withreference to Fig. 2,thiswinding is of the star-connected three phasetype. The winding is shown as energized from a three phase supply line`21 through ay suitable switch 22.

When the winding 20 is energized a moving field is established in 'thecore 14, this fleldmovingin the direction ofthe arrow 23 shown in Figs.5 and 6. With reference to Figs. 5 and 6, as the field moves in thedirection indicated, the pole designated by line a will increase whilethe pole represented by line Will decrease by a proportionate amount.Finally the pole c will dis appear altogether and at that instant thepole a will be equal to the pole b. At the neXt instant, however, thepole Z) Will start to decrease While a new pole Will be formed at theupper extremity of the co`ref. 'It will be observed that the sum of theflux remains always constant and for this reason the pulling :torceexerted upon the arin-ati'i-re 17 'willr vary substantially inverselyproportional to the distance between the armature 17 and the core 111.When these members ar'e in engagement the pull Will remain constant andvibration and chattering of the armature 17 Will thus be "eliminate-d.

Vith reference to Figs. 1, 2, and G, the Winding establishes a movingi'eld which starts Eat 'one end of the Acore fand ends at the other end.In cases Where it is desired to have a continuous rotating field, I haveprovided the construction shown in Figs. 3 and 4'. In this magnet apolyphase Winding 9.4 is secured in slots in a laminated core 25, thiscore being -iiXedly supported by a suitable bracket 26. In thisconstruction ya vshaft 27 is slidably mounted in bearings 28 and 29formed respectively -in brackets 30 and 526-. A circulalrly laminatedarmature 31 is formed -in the shape of a ldisk` or plate and is rigidlysecured to the shaft 27. Up'on .energization of the Winding 24, thearmature ..31 will be Aattracted toward the core with a Vpullsubstantially inversely proportional to the square of the distancebetween the armature and core, and any suitable device attached to ftheshaft -27 will be moved `accordingly. The magnet s'hown in Figs. 3 and 4is more powerful for a short stroke than the'inagnet shown in Figs. 1land 2 and for this reason the continuous Afield maginet is especiallyyapplicable for use as a magnetic brake, While the magnet shown in Figs.1 and 2 is applicable for use with lmany forms l of switching apparatus,since a larger stroke can begobtazined With this form of magnet.

While l have sho'wn the windings `Q0 Yand 21 as being secured in slotsin the stator members, it should -be understood that it is not necessarythat the Winding be .all in the stator member. It would 4be y:possibleto 'have 'slots-in Iboth the core of the lstator Imember and intheVVarmature member with windings `in each set 'oflslots Again, 'theentire Windying could be mounted in the armature member, leavingthecorec'or stator member with no slotsl Whatever. llVith lreferencepartieularly to the magnet shown in :Figs fl and 2 it should be noted`also itha't the. radins of vlargeWindii'ig ea-n be 'usedvvhile theventi r rcal length offfthe Yarmature'may'i-be small.

It should be understood that the invention is not limited to a device inWhich an armature is attracted to a core. The Winding may, for instance,be placed on a flat horizontal core and the device used as a magneticchuck.

lVhat I claim as neuT and desire to secure by Letters Patent of theUnited States, is:-

1. An alternating current electromagnethaving opposed 'magnetic members,and a distributed, polyphase winding arranged to establish a flux whichpulls the members together and which moves transversely of the directionof pull of said magnet.

2. An alternating current electromagnet comprising a core, a distributedpolyphase Winding secured `across the face vof said core having 'a face,and a magnetic member movable normal t'o the face lof said core, saidWinding being arranged to establish a substanti-ally constant flux.vhich 'nieves transrversely of the direction of movement of saidmember.

3. An alternating current electromagfnet vcomprising a core, havingslots therein, a distributed, polyphase Winding secured in said slots,and a magnetic member movable into engagement with ysaid core, saidWinding being arranged to `establish a fluir which constantly movessubstantially at right in a .plane substantially perpendicular to.

the ldirection of movement of said member.

5. An alternating 'current electromagnet 'comprising a core having aface, an armature mounted in opposing parallel relation With the face ofsaid core, a starrconneeted, three phase Winding extending across thevface 'of said core, said Winding being arranged a) 'establish asubstantially Constant iiux Awhich pulls the members together and whichvmoves ftrar1s`vers'ely ythe 'face `of said core. 'y y l 6. Analternating current electromagnet comprising a yfied support, a coresecured to said support, an armature pivotally mounted on said support,to be movable substantially perpendicularly of the face of said core, astar-connected three phase Winding arrangedacross the face of said core,'said Winding being arranged t0 es tablish a luX moving transverselyWith respect 'to the directionof movement Acffsiiid armature wherebysai'd armature is attracted teward sa'id core With a oree ysubstantiallyLinversely 'proportional to fthe Vsquare of the distance between thecore and the armature.

7. An alternating current electromagnet comprising a core having aconcave face, a distributed, polyphase winding on said core, an armaturepivotally mounted to be movable toward and away from the face of saidcore, the side of said armature nearest said core being convex forregistering relation with the concave face of said core, said windingbeing arranged to establisli a linx moving always in one directionacross the face of said core.

8. An alternating current electroma net comprising a core having aconcave ace, slots in the concave face of said core, a distributedpolyphase winding in said slots, an armature pivotally mounted to bemovable toward and away from the face of said core, the side of saidarmature nearest said core being convex for registering relation withthe concave face of said core, a starconnected, three phase winding onsaid core, said winding being arranged to establish a flux which movesacross said core substantially transversely with respect to thedirection of movement of said armature, the sum of said flux beingconstant whereby said armature is attracted to said core with asubstantially constant force.

In witness whereof, I have hereunto set my hand this 11th day ofJanuary, 1929.

PANFILO TROMBETTA.

